Montserrat Volcano Observatory

Daily Report
Report for the period 16:00 3 January
to 16:00 4 January 1997
The current alert level is ORANGE

Growth of the October 1 dome continues to generate rockfalls and small pyroclastic flows. There was also shallow VT earthquake activity under the crater area, the first since activity on the October 1 dome restarted in late December. Areas outside of the Tar River valley are not currently threatened by this activity, although anywhere downwind of the volcano will be affected by light ashfall. A rapid escalation in activity is possible and could have serious consequences for much of the evacuated areas. Everyone should remain vigilant and follow the alert procedures. There is no access to zone A/B and only limited access to zone C/D.

Seismic activity was dominated by rockfalls and shallow VT earthquakes. 78 rockfall signals were recorded today, a slight decrease from yesterday. All the rockfalls are probably generated by growth of the October 1 dome. The size of the rockfalls was slightly reduced compared to those recorded in the last two days. Shallow VT earthquake activity resumed during this reporting period, with 53 VT earthquakes recorded. These were in the first swarms of shallow VTs since December 21, when activity resumed on the October 1 dome. The VT earthquakes occurred in three distinct swarms, from 6 to 8 pm last night, from 4:30 until 6 am today and from 2:50 pm until the end of the reporting period. The signals from these VTs are similar to those from the shallow VT swarms that dominated the seismic records during November and early December. Like those events, the current ones are located under the crater area, but at slightly deeper depths, 2 to 3 km. The level of activity is much less than that recorded during the peak of activity in mid-December.

Visibility has been poor for most of the day, with the crater area covered in cloud. Rockfalls and small pyroclastic flows were observed during brief periods of partial visibility this morning. Small ash clouds were generated by rockfalls throughout the day. These drifted to the west forming a diffuse low-level ash plume. Satellite observations detected the plume out to a distance of over 200 miles from Montserrat

GPS measurements were made on the "BIGNET" network around the volcano.

The Sulphur Dioxide flux in the gas plume, measured using COSPEC, was about 400 tonnes per day. This is a slight increase over recent measurements.

Sharon Teebenny and Uche Osuji from the Seismic Research Unit, University of West Indies, arrived today to take up their duties at MVO.

Montserrat Volcano Observatory